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Proxy Server PROXY SERVER Proxy Server What is a Web Proxy? A proxy is a host which relays web access requests from clients Used when clients do not access the web directly Used for security, performance browser logging, proxy accounting web and Proxy Server What is Web Caching? Storing copies of recently accessed web pages Pages are delivered from the cache when requested again Browser caches Proxy caches Proxy Server Why Cache? Shorter response time Reduced bandwidth requirement Reduced load on servers Access control and logging Proxy Server Popular Proxy Caches Apache proxy MS proxy server WinProxy Squid Squid is popular because configurable and free Many others it is powerful, Squid Setup SQUID SETUP Squid Setup Obtaining Squid Source code (in C) from www.squid-cache.org Binary executables Linux (comes with RedHat and others) FreeBSD Windows Pre-installed in Fedora/Enterprise Linux Squid Setup Basic Settings Edit the /etc/squid/squid.conf file to configure squid Configuration options: Disk Cache size and location Authentication Allowed Hosts Any other access restrictions (sites, content, size, time of access etc.) using ACL service squid start/stop/restart QUESTIONS? Email EMAIL Email Mail Architecture Internet Mail Server Mail Client Mail Server Mail Client Email Mail Architecture Email Mail Architecture Simple Mail Transfer Protocol (SMTP) is used to transfer mail between Mail Servers over Internet Post Office Protocol (PoP) and Interactive Mail Access Protocol (IMAP) is used between Client and Mail Server to retrieve mails The mail server of a domain is identified by the MX record of that domain Popular Mail Servers Sendmail/Postfix Microsoft Exchange Server IBM Lotus Sendmail Setup SENDMAIL SETUP Mail Server Setup Sendmail Configuration Daemon: sendmail Configuration File: /etc/mail/sendmail.mc Edit the following lines LOCAL_DOMAIN(`localhost.localdomain')dnl (Replace localhost.localdomain by the domain name for which the mail server is being configured) DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl (comment this line by adding dnl at the start of the line) dnl MASQUERADE_AS(`mydomain.com')dnl (remove dnl & replace mydomain.com by the domain name) Sendmail Setup Sendmail Configuration Add the range of IP addresses of your network in access file (e.g. 172.31. Relay) Run “make –C /etc/mail” command to compile sendmail.mc and generate sendmail.cf file. Restart sendmail and watch for errors Sendmail Setup PoP & IMAP Server PoP3 & IMAP Server can be started using dovecot server. (service dovecot start) QUESTIONS? VoIP VoIP APPLICATIONS VoIP What is VoIP The packetization and transport of classic public switched telephone system audio over an IP network. The analog audio stream is encoded in a digital format, with possible compression, and encapsulated in IP for transport over your LAN/WAN or the public Internet Modes of Operation: - PC to PC - PC to Telephone - Telephone to PC - Telephone to Telephone VoIP VoIP Protocols H.323 (ITU-T) SIP (IETF) VoIP H.323 Architecture H.323 Terminal Gateway Gatekeeper Multipoint Control Units (MCU) VoIP SIP SIP is a text-based protocol similar to HTTP and SMTP, for initiating interactive communication sessions between users SIP is an application-layer control (signaling) protocol for creating, modifying and terminating sessions with one or more participants SIP can be used with different transport protocols, it doesn't even require reliable transport protocols A simple SIP client can be implemented using only UDP VoIP SIP Architecture QUESTIONS?